We are fairly new to the Catholic Church. My children, ranging from age 11 to age 1, have recently pretended to be at Mass in their play. They’ll do things like take a children’s Bible and put it up high and then go behind a side table to have a reading. Or sometimes they’ll be a little more elaborate and have one person be the priest and the others will say the responses and prayers. I know children learn and process things through play. I was just wondering if there anything wrong/in bad taste/or sinful about this kind of play.

No. In fact, it is a longstanding custom in many Catholic families for children to set up pretend Masses over which they pretend to preside. Many a priest has first felt a vocation to the priesthood from such childhood play.